Wire Splice Symbol
Definition: The Wire Splice symbol represents a permanent electrical connection between two conductor ends in a wiring diagram, used to denote an in-line joint where two wire segments are joined mechanically and electrically by crimping, soldering, a wire nut, or an in-line splice connector, creating a single continuous conductor without an accessible terminal point.
Also known as: inline splice, wire joint, conductor splice, cable splice, wire connection, butt splice.
What the Wire Splice symbol means
The Wire Splice symbol identifies a point on a conductor where two wire segments are permanently joined in a wiring diagram. Unlike a wire junction node (which shows multiple conductors branching from a single point), a wire splice is an in-line joint connecting exactly two wire ends—terminal A and terminal B—on the same conductor path.
In electrical installation drawings the splice symbol alerts the installer that a connection must be made at that physical location using a listed splice method (crimp, wire nut, heat-shrink butt connector, or direct solder joint) and that the splice must be housed in an accessible junction box per NEC 300.15 unless a listed direct-burial or concealed-splice fitting is specified.
How to identify the Wire Splice symbol
The symbol is drawn as a small filled or outlined X, a small dot on a single wire, or a bar-and-dot connector icon placed along a conductor line, with terminals A and B at the two wire ends entering the symbol from opposite directions (left and right). This in-line placement on a single conductor distinguishes it from the T-junction or X-junction of the wire node symbol.
Function in a circuit
A wire splice creates a mechanically and electrically continuous conductor from two separate wire ends. Common splice methods include: butt crimp connectors (copper or insulated), wire nuts (twist-on, for branch splices), heat-shrink solder sleeves (for moisture-resistant connections), and direct solder-and-tape joints. The splice must meet the same current-carrying capacity and insulation rating as the conductors it joins, and must not introduce significant resistance (< 1 mΩ for a quality crimp splice).
Standards: IEC vs ANSI
| IEC 60617 | IEC 60998-2-3 covers in-line connecting devices (butt splices) for use with copper conductors; IEC 60352-2 covers solderless crimped connections. The wire splice is represented in IEC 60617 schematics as a generic connection point on a single conductor run. |
|---|---|
| ANSI/IEEE 315 | UL 486A-B covers wire connectors (including butt splices) for copper conductors; NEC Article 300.15 requires that all splices be made in accessible boxes unless the splice fitting is listed for direct burial or concealment. NEC 110.14(B) requires all splices to be mechanically and electrically continuous and to restore insulation to the same rating as the original conductor. |
| Key difference | IEC 60998 and UL 486 are functionally equivalent standards for splice connectors; IEC focuses on the connector product requirements, while NEC focuses on installation location (accessible box) and method acceptability. Both require the splice to restore the conductor's full current-carrying capacity. |
Terminals / pins
| Pin | Name |
|---|---|
| a | A |
| b | B |
Typical values
AWG range: matched to conductor gauge (common sizes: AWG 22–6 for butt splices); voltage rating: 300–600 V (insulated connectors); temperature rating: 60–105°C; contact resistance: < 1 mΩ (quality crimp); pull-out force: per UL 486A-B requirements for conductor gauge.
Where the Wire Splice symbol is used
- Junction boxes where branch-circuit conductors are lengthened using butt-splice connectors
- Automotive wiring harnesses where conductor segments are joined with heat-shrink solder sleeves
- Appliance service leads where a damaged conductor section is repaired with a listed in-line splice
- Underground direct-burial cable splice points using UL-listed gel-filled in-line splice connectors
- Panel feeder extensions where new wiring adds length to an existing circuit
- Luminaire flex connections where factory-installed leads are spliced to branch-circuit conductors
Example
In a residential panel extension drawing, the wire-splice symbol appears on a 12 AWG circuit conductor at a junction box where the original 10 ft run is extended by 6 ft to reach a relocated outlet; terminals A and B show the two wire ends joined by a yellow insulated butt-crimp connector rated 600 V, 10 AWG–14 AWG, housed inside a listed 4-inch square junction box.
Key facts
- The Wire Splice symbol has two terminals: A and B, representing the two conductor ends that are permanently joined at the splice point.
- A wire splice creates a single electrically continuous conductor from two wire ends; it carries the same current as the conductors it joins and must not be a point of increased resistance.
- NEC Article 300.15 requires all splices to be accessible in a listed junction, pull, or outlet box unless the splice is made using a listed direct-burial or in-wall splice kit.
- A quality crimped butt-splice connector introduces less than 1 mΩ of contact resistance; a poor solder joint or loose crimp can cause resistance heating, voltage drop, and eventual failure.
- Conductor insulation at a splice must be restored to the same voltage and temperature rating as the original conductor insulation—bare or under-insulated splices are a leading cause of electrical fires.
- Underground cable splices must use connectors specifically listed for direct burial per NEC 300.5(E) and UL 486, typically including a gel-filled or resin-filled housing to exclude moisture.
- The wire splice symbol differs from the wire junction node: a splice is an in-line joint of exactly two conductors on one path; a junction node is a point where three or more conductors branch from a single node.
Frequently asked questions
What does the wire splice symbol mean in a wiring diagram?
The wire splice symbol represents a permanent in-line joint between two conductor ends. It indicates that two wire segments are connected at that location using a listed splice method (butt crimp, wire nut, solder, or heat-shrink splice connector), creating a single continuous conductor.
What is the difference between a wire splice and a wire junction?
A wire splice joins exactly two conductor ends in-line (A to B) on a single continuous path. A wire junction (node) is the point where three or more wires branch from a common node. A splice continues one conductor; a junction creates a branching network.
Does a wire splice need to be in a junction box?
Yes, per NEC Article 300.15, all splices must be made inside an accessible junction box, pull box, or device box unless a listed direct-burial, in-wall, or in-ceiling splice connector is used. Splices may not be concealed inside walls without a listed fitting.
What methods can be used to make a wire splice?
Listed wire-splice methods include: insulated butt-crimp connectors, wire nuts (for branch splices), heat-shrink solder sleeves, gel-filled in-line splice connectors (for direct burial), and soldered joints covered with rated heat-shrink tubing. All methods must comply with NEC 110.14(B) and use listed components.
What standard governs wire splice connectors?
UL 486A-B (wire connectors for copper conductors) and UL 486C (for aluminum conductors) are the primary North American listing standards. IEC 60998-2-3 covers in-line connecting devices internationally, and IEC 60352-2 covers solderless crimped connections.
How many terminals does the wire splice symbol have?
The wire splice symbol has two terminals: A and B, representing the two wire ends that are joined at the splice point. The splice is an in-line connection; both terminals are on the same conductor path.
What is the IEC vs ANSI difference for wire splice symbols?
IEC 60617 represents a splice as a generic in-line connection marker on a conductor; ANSI/NEC diagrams use a butt-splice indicator icon or small annotation on the conductor line. Both convey the same meaning—the conductor is spliced at that point. Installation requirements differ: IEC focuses on connector product standards (IEC 60998) while NEC specifies accessible-box requirements (Article 300.15).
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